The invention relates to an apparatus applied in an optical disc drive and a related method, and more particularly, to a defect estimating apparatus and a related method.
For several years, optical disc drives have been considered standard equipment for personal computers. Generally, optical disc drives are utilized for recording information onto optical discs and for reading information stored on the optical discs or both. In some examples of related art, optical disc drives are designed to read or write data upon different kinds of optical discs, such as compact disc (CD) and digital versatile disc (DVD). In addition, except for some write once optical disc e.g. CD-R and DVD-R, the optical disc drives are capable of rewriting data onto certain optical discs e.g. CD-RW and DVD-RW.
When an optical disc drive is recording information onto a defect area of an optical disc, the information recorded onto the defect area cannot be read back correctly. Therefore, it is necessary to detect if a defect exists on the optical disc when the information is being recorded. Please refer to FIG. 1. FIG. 1 is a schematic diagram of a related art that presents a defect estimating apparatus 10 applied in an optical disc drive. The defect estimating apparatus 10 of the related art comprises a defect detector 12, a frame counter 14, and a computing module 16. If the defect detector 12 determines that a defect exists in a predetermined region, the defect detector 12 outputs a defect value to the computing module 16. The computing module 16 accumulates the defect values as they are received in the predetermined region. Utilizing the accumulated defect values, the computing module 16 generates a defect estimation value of the predetermined region. If the defect estimation value is greater than a threshold value, the optical disc drive will skip the predetermined region in favor of recording data into another region. The frame counter 14 is utilized for counting a plurality of frames of the data to be written onto the optical disc, and for outputting a frame number to the computing module 16 accordingly. The computing module 16 is capable of determining the start and the end of the predetermined region according to the frame number transmitted from the frame counter 14 and generate defect estimation value according to the defect value from the defect detector 12. When the computing module 16 receives a frame number corresponding to the end of the predetermined region, the computing module 16 will reset the defect estimation value to zero, and then begins the process of accumulating defect values for generating a defect estimation value for the next region.
Although the architecture of the defect estimating apparatus 10 of the related art is very simple, the effect of a defect may be undervalued or overvalued by the defect estimating apparatus 10 of the related art. Take the Compact Disc (CD) as an example. FIG. 2 is a schematic diagram of an encoder 30 of the related art applied in a CD drive. The encoder 30 of the related art comprises a C2 encoder 32, unequal-length delay lines 34, and a C1 encoder 36. In the beginning, twenty-four 8-bit symbols are interleaved and then transmitted to the C2 encoder 32. The C2 encoder 32 encodes the twenty-four 8-bit symbols, and then outputs twenty-eight encoded symbols. Next, the twenty-eight encoded symbols are delayed by different time intervals, such as 0, 1D, 2D, . . . , 27D, where D denotes the length of four input timings. Finally, the C1 encoder 36 encodes the received symbols, and outputs thirty-two encoded symbols. Please refer to FIG. 3 and FIG. 4. FIG. 3 is a schematic diagram of a sector 40 outputted by the C2 encoder 32 shown in FIG. 2. FIG. 4 is a schematic diagram of the sector 40 received by the C1 encoder 36 shown in FIG. 2. Since the unequal-length delay lines 34 shown in FIG. 2 delay the symbols inputted at the same time by different time intervals, the length of the sector 40 shown in FIG. 3 is extended from 98 frames to 206 frames as shown in FIG. 4. Referring FIG. 4, a symbol 42 of the sector 40 will be recorded onto the CD with twenty-seven symbols of other sectors in a frame, and the symbols 44, 46 of sector 40 will be recorded on to the CD with twenty-six symbols of other sectors in a frame. If a defect exists in the region for recording the first frame of the sector 40, only symbol 42 is impacted by the defect. However, if a defect exists in the region for recording the fifth frame of the sector 40, two symbols 44, 46 are impacted by the defect.
It is clear that the impacts of the different defects, even those that have the same size but are in different locations, are different. As a result, the defect estimation value generated by the defect estimating apparatus of the related art cannot precisely represent the corresponding impact of a defect.